The present invention relates generally to compressors of the type having a cantilever mounted reed valve that controls the flow of refrigerant through a respective port communicating with the compression chamber of the compressor and, more particularly, to means for mounting the valve in a manner insuring proper indexing of the valve, i.e., orientation of the valve so as to precisely cover its associated port.
In general, positive displacement refrigeration compressors operate to compress refrigerant by drawing a substantially fixed volume of refrigerant through a suction port into a compression chamber, compressing the refrigerant by means of decreasing the volume of the compression chamber, and discharging the compressed refrigerant through a discharge port to a refrigeration system. In many compressor designs, particularly reciprocating piston compressors, the suction and discharge ports are simultaneously in communication with the compression chamber and, therefore, valving is required to insure proper flow of the refrigerant into and out of the compression chamber. Furthermore, discharge valves function to prevent reverse flow of refrigerant into the compression chamber when it is at a lower pressure than the refrigeration system.
One type of valving commonly employed in compressors of the type herein described is a cantilever mounted reed valve, wherein one end of the valve is attached to the compressor crankcase and the other end is positioned over a respective suction or discharge port. Consequently, the unattached end is free to open and close with respect to a valve seat surrounding the port opening. For proper seating of the valve onto the valve seat, it is essential that the valve be mounted in a manner to insure proper valve indexing, i.e., orientation of the unattached valve end precisely over the associated port. To this end, various and several methods of mounting reed valves have been utilized in prior art compressors.
Generally, prior art methods of cantilever mounting a reed valve in a compressor are designed to secure the mounted end of the valve against axial movement, and to prevent any rotational movement of the valve about the mounted end which would result in improper valve indexing. One common method of preventing rotation of the reed valve is to provide two spaced apertures in the mounting end of the valve, through which two corresponding locating pins or fasteners are received. For instance, where the mounting end of the valve is axially retained intermediate the top surface of the compressor crankcase and the bottom surface of a valve plate or cylinder head, a pair of locating pins are received through the spaced apertures. Likewise, when the reed valve is mounted directly onto the top surface of the valve plate, or onto the outer surface of the compressor crankcase or cylinder head in a hermetic compressor, the mounting end of the valve may be attached thereto by means of a pair of spaced rivets or screws. Accordingly, the head of the fastener axially retains the mounting end of the valve while spacing between fasteners properly indexes the opposite end of the valve over the valve seat.
One disadvantage associated with the aforementioned valve indexing method is the need to precisely locate and provide two locating pin holes or mounting holes for each valve. In most instances a single fastener will axially retain the mounting end of the valve, but the second fastener is required for valve indexing. Consequently, two locating pins or fasteners will also be required for each valve. Not only does the additional pin or fastener increase the manufacturing and materials cost of the compressor, but marginal costs are associated with the increased complexity and space requirements of such an arrangement.
Another prior art valve mounting arrangement provides a transverse cut or slot in the surface to which the valve is to be mounted. The slot is cut so as to define a boundary for the elongated reed valve, whereby the valve is properly indexed when situated in the slot. The mounting end of the valve may then be attached to the mounting surface by means of a single fastener, such as a screw or rivet. One disadvantage of this mounting method is the possibility that, during operation, the intermediate, unattached valve portion will contact the sidewall of the slot, thereby impeding free operation of the unattached end of the valve. Another disadvantage of this mounting method is the costs and limitations associated with providing the necessary indexing slot. Either a precision milling operation is required to machine the slot in a cast iron part, or a more expensive sintered or powdered iron material is required to cast the part with the slot already formed.
In a hermetic rotary compressor assembly to which the present invention is particularly applicable, an electric motor and compressor mechanism are located in a hermetically sealed housing. The electric motor is connected to a crankshaft which includes an eccentric portion located within a compression chamber bore defined by a compressor cylinder block. The crankshaft is journalled for rotation by a main bearing and an outboard bearing which define the axial ends of the compression chamber. A roller located within the compression chamber is mounted on the eccentric portion of the crankshaft and is driven thereby. The roller cooperates with a sliding vane to compress refrigerant within the chamber for discharge out respective discharge ports through the main and outboard bearings A discharge valve assembly, comprising a reed valve and an overlying valve retainer, is mounted on the axially outer surface of the main and outboard bearing in operative association with a respective discharge port. In this arrangement, it is desired that the main and outboard bearings be of cast iron and that the valve assemblies be simply and inexpensively mounted to the bearings in a manner to insure proper indexing of the valves.
Accordingly, it is desired to provide cantilever mounting and proper indexing of a reed valve in a compressor, which overcomes the aforementioned problems and disadvantages of the prior art.